[dev.regabi] cmd/compile: make copyExpr return *ir.Name directly
[dev.regabi] cmd/compile: make copyExpr return *ir.Name directly

copyExpr just calls copyExpr1 with "clear" is false, so make it return
*ir.Name directly instead of ir.Node

Passes toolstash -cmp.

Change-Id: I31ca1d88d9eaf8ac37517022f1c74285ffce07d3
Reviewed-on: https://go-review.googlesource.com/c/go/+/280714
Trust: Cuong Manh Le <54b4457f1dff6823379654eb5867596497ba782f@gmail.com>
Run-TryBot: Cuong Manh Le <54b4457f1dff6823379654eb5867596497ba782f@gmail.com>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Matthew Dempsky <e56ac2c500064424afac424d4b5e53bd0570a731@google.com>

golang/go,cloudflare/go,CAFxX/go,cloudflare/go,cloudflare/go,golang/go,CAFxX/go,golang/go,CAFxX/go,nawawi/go,cloudflare/go,cloudflare/go,cloudflare/go,nawawi/go,CAFxX/go,CAFxX/go,nawawi/go,nawawi/go,golang/go,nawawi/go,cloudflare/go,nawawi/go,golang/go,nawawi/go,CAFxX/go,golang/go,CAFxX/go,golang/go,golang/go,cloudflare/go,CAFxX/go,nawawi/go